Ring connector for implantable medical devices

ABSTRACT

An electrical contact for use in the header assembly of an implantable tissue stimulator includes a metal housing having a base and a sidewall where the opening in the base is adapted to receive the terminal of a medical lead therethrough. An electrical contact support member is welded to the edge of the sidewall and affixed to the support member are a plurality of spring members that are tangent to an imaginary circle whose diameter is slightly less than the outside diameter of the lead terminal contact rings. When the contacts are axially aligned in the device header, the terminal of an electrical lead may be longitudinally inserted into the header to establish electrical contact with device feedthrough wires that are joined to the electrical contacts in the header.

BACKGROUND OF THE INVENTION

[0001] I. Field of the Invention

[0002] This invention relates generally to implantable electronic tissuestimulating apparatus of the type including a pulse generator that iscoupled through a medical lead to target tissue, and more particularlyto the design of electrical contacts used in a header of such a pulsegenerator to mechanically and electrically couple the pulse generator'sinput/output pins to a proximal terminal of a medical lead.

[0003] II. Discussion of the Prior Art

[0004] Over the past 30 years great strides have been made in increasingthe functional performance of and decreasing the physical size ofimplantable medical devices, such as those designed for cardiac rhythmmanagement and neural stimulation. Generally speaking, currentstate-of-the-art implantable medical tissue stimulating devicesincorporate a battery power supply and a microprocessor-based controllerthat is designed to control a pulse generator, causing it to issuepulses at times determined by the microprocessor-based controller. Thepulses are conveyed to target tissue on or in the heart by means of oneor more medical leads having sensing/stimulating electrodes at a distalend and the electrodes are connected by lead conductors to electricalcontacts on a connector pin located at the proximal end of the lead. Thelead connector connects the lead to the pulse generator.

[0005] While a variety of lead connectors have been devised, a majorimprovement in lead connectors has been the low profile, in-line bipolardesign. An in-line connector places both electrical terminals on asingle lead pin, with an insulating barrier separating the anode contactfrom the cathode contact. To facilitate compatibility between pulsegenerators and leads of differing manufacturers, standards have beendeveloped. More particularly, a collaborative effort between IEC andInternational Standards Organization has defined the parameters of alow-profile connector referred to as IS-1 for unipolar and bipolar leadsand DF-1 for defibrillator leads. Additionally, there is ongoing work todevelop AAMI and potentially ISO standards for connectors for tripolarand quadrapolar leads.

[0006] As those skilled in the art appreciate, the lead connector mustbe mechanically and electrically secured to the implantable device in away that remains secure following implantation, but which can be readilydetached if and when it becomes necessary to install a new pulsegenerator. The Persuitti et al. U.S. Pat. No. 6,044,302 describes aconnector port for an implantable pulse generator that can accommodate aplurality of in-line lead terminal pin having multiple contacts. In the'302 patent, a lead port has one or more connector blocks each includinga set screw to lock the lead connector in contact with the connectorblock. The connector blocks are, in turn, connected to a feed-throughwire. A single elastomeric seal is provided within the port such thatwhen the connector pin is inserted therethrough, it precludes ingress ofbody fluids into the bore in the header. It is also known in the art toprovide sealing rings on the lead terminal connector itself for creatinga fluid impervious seal upon insertion of the lead's terminal into aconnector port. In this regard, reference is made to the Hawkins et al.U.S. Pat. No. 6,029,089.

[0007] Copending application Ser. No. 10/222,151 filed on Aug. 16, 2002,and entitled “Connector Port Construction Technique for ImplantableMedical Device”, which application is assigned to the assignee of thepresent application, there is described a connector port for animplantable medical device that is capable of accommodating multiplefeedthrough wires and lead connector contacts and that is small in size,easy to assembly and which exhibits a low insertion force. The leadconnector contacts described in the aforereferenced application(referred to herein as a toroidal spring design) comprise a metalhousing having a circular bore formed through the thickness dimensionthereof The wall defining the bore includes an annular recess forcontaining a canted-coil spring that is formed as a ring. A number ofsuch electrical contacts are concentrically aligned in a molded plasticheader with elastomeric seals disposed between each such contact. Afeedthrough wire on the pulse generator is then welded to the housingcontaining the canted-coil spring. Upon insertion of a lead terminal,the spring is spread to receive a terminal contact therein and the coilspring engages the terminal contact at a multiplicity of points aroundits circumference.

[0008] The use of the currently available spring design is not optimal.The toroidal spring “floats” within the bore of the housing comprisingthe contact and makes connection between the terminal and spring, and inturn, between the spring and contact housing only through physicalinterference. This can lead to an unnecessarily high resistanceconnection between the connector contact member and the contacts on thelead's terminal pin. Other spring designs for this application are toolarge to fit within the required space or also float within theirhousing.

[0009] It is accordingly a principal object of the present invention toprovide a small, improved, cost effective connector contact for use inthe header of an implantable pulse generator and which provides a morepositive connection between a feedthrough wire of the pulse generatorand a lead terminal.

SUMMARY OF THE INVENTION

[0010] The present invention provides an electrical connector contactfor use in the header assembly of an implantable cardiac rhythmmanagement device for mating with a terminal pin of a tissuestimulating/sensing lead. The contact connector comprises a metalhousing that has a base and a sidewall. A central opening in the base issized to receive a terminal pin of a medical lead therethrough with apredetermined non-contact clearance. A plurality of spring members areattached to an electrical contact support member where the supportmember has an outside shape permitting placement on an exposed edge ofthe sidewall of the housing. The spring members are attached to thecontact support member such that they project inwardly of the insideopening of the electrical contact support member to provide aninterference fit with a lead terminal pin that is inserted through theopening in the base of the housing and through the electrical contactsupport member.

[0011] In one embodiment, the spring members are generally shaped toprovide an interference fit with minimal drag, allowing compressionthereof when the terminal pin of the tissue stimulating lead isinserted. In an alternative embodiment, the electrical contacts are bentcylindrical bars having one end welded to the contact support member anda straight section oriented tangent to a circle that is centered withrespect to the opening in the base and of a lesser diameter than theopening in the base.

DESCRIPTION OF THE DRAWINGS

[0012] The foregoing features, objects and advantages of the presentinvention will become apparent to those skilled in the art from thefollowing detailed description of a preferred embodiment, especiallywhen considered in conjunction with the accompanying drawings in which:

[0013]FIG. 1 is an isometric view of a ring connector comprising a firstpreferred embodiment;

[0014]FIG. 2 is a cross-sectional view taken along the line 2-2 in FIG.1;

[0015]FIG. 3 is a cross-sectional view taken along the line 3-3 in FIG.2;

[0016]FIG. 4 is an isometric view of a contact ring used in the assemblyof the embodiment of FIG. 1;

[0017]FIG. 5 is a cross-sectional view along the line 5-5 in FIG. 4;

[0018]FIG. 6 is an isometric view of an alternative preferred embodimentof the invention;

[0019]FIG. 7 is a cross-sectional view taken along the line 7-7 in FIG.6;

[0020]FIG. 8 is a cross-sectional view taken along the line 8-8 in FIG.7; and

[0021]FIG. 9 is an isometric view of one of the contacts used in theembodiment of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Referring to FIG. 1, there is shown a ring connector for use inthe header of an implantable tissue stimulator, such as a cardiacpacemaker or an automatic implantable cardiac defibrillator. The ringconnector may be used in the manner fully described in theaforereferenced co-pending application Ser. No. 10/222,151, which ishereby incorporated by reference. It is seen to comprise a housingmember 12 made of a suitable metal. It had a base 14 and a sidewall 16,where the base 14 includes an opening 18 that is of a predetermined sizeslightly larger than the diameter of a lead terminal that is to beinserted therethrough. As a result, there is a predetermined non-contactclearance between the opening and the lead terminal. Resting atop theexposed edge 20 of the metal contact housing 12 is a washer-like plate22 that is welded to the exposed edge 20 of the housing. The centralopening 24 of the washer 22 is generally sized such that a lead terminalwill also have a non-contact clearance with the washer 22.

[0023] As seen in the cross-sectional view of FIG. 2, a spring contactmember 26 is welded to the washer 22. Referring momentarily to FIG. 4,the spring contact member 26 is made of a suitable metal, such as MP35N.In a preferred form, the contact members are formed with the ring 28 ina stamping and bending operation.

[0024] The cross-sectional view of FIG. 5 shows that the contacts 30 ofthe member 26 are generally shaped to provide interference with minimaldrag, having a straight back portion 32 that is generally perpendicularof the plane of the ring 28 and an arcuate front portion 34. Thecurvature of the front portion 34 is such that it is tangent to animaginary circle that is of a lesser diameter than the opening in member28 and the openings 18 and 24 seen in FIG. 1.

[0025] Referring next to the cross-sectional view of FIG. 3, it can beseen that the contact member 26 of FIG. 4 is welded at pointsrepresented by the black dots 38 in the drawing to the washer 22 andthat the contacts 30 encroach into the opening defined by the apertureof the contact support member 26. The tolerances are such that when alead terminal is inserted through the opening 18 in the housing member12 with a predetermined force, it will deflect the springs 30 which thenintimately engage a contact ring on the lead terminal to establishelectrical contact at a multiplicity of points, resulting in a lowimpedance connection.

[0026] While the embodiment described illustrates six contacts 30 on thespring contact member 26, a greater or a fewer number of such contactsmay be utilized. As a minimum, however, there should be at least threesuch contacts, but with six such contacts being preferred. The contacts30 will be deflected as the lead terminal is inserted through the ringconnector 10. While the embodiment reflected in FIGS. 1-5 show thecontact ring 28 spot-welded to the underside of washer 22, it is alsopossible to insert the contact ring 28 into the housing with thecontacts 30 projecting upward from the base 14.

[0027] FIGS. 6-9 illustrate an alternative embodiment of the ringconnector of the present invention. The ring connector, indicatedgenerally by numeral 40, again comprises a metal contact housing 42having a sidewall 44 supported on a base 46. The base has an opening 48formed therethrough that is sized to receive a lead terminal withnon-contact clearance. Again, the size of the opening 48 is slightlygreater than the diameter of a ring contact on a medical lead to beinserted through that aperture. The aperture 48 is preferably beveled,as at 50, to facilitate or guide the insertion of a lead's terminaltherethrough. Welded to an exposed edge 52 of the wall 44 is a contactplate 54 in the form of a washer having an opening 56 that is seized toreceive a lead terminal with non-contact clearance. At regularintervals, e.g., every 60°, a small hole, as at 58, is drilled throughthe contact support member 54. Fitted into each of these holes is oneend 60 of a generally bent cylinder contact 62. An isometric view of onesuch bent cylinder contact is shown in FIG. 9.

[0028] Referring to FIG. 8, before being welded in place within theholes 58, the contacts 62 are aligned in a manufacturing jig (not shown)so that the straight section 66 of the bent cylinder is tangent to animaginary circle represented by the broken line 68 in FIG. 8 and bentend portion 64 is directed away from that circle. When a lead terminalis inserted through the contact member assembly 40, the cylindrical barcontact 62 will be deflected so as to press against a contact surface ofthe lead's terminal to establish a low resistance path between the pulsegenerator (not shown) that attaches to the housing 42 and the aforesaidlead contact surface.

[0029] When the ring contact assemblies 10 and 40 of FIG. 1 or FIG. 6,respectively, are axially aligned in the header of an implantablemedical device of the type concerned here, they electrically couple thedevice's high or low voltage output to a corresponding medical leadterminal. No outside mechanical actuation or tools are required, such asset screws or Allen wenches. In addition, the contact assemblies of thepresent invention are less costly than known prior art ring contactarrangements.

[0030] The physical geometry of the contacts disclosed herein is quitedifferent from known prior art approaches. The spring tabs or bentcylinders of the present invention, instead of the canted toroidalsprings of the prior art, yield improved results. The prior artcompetitive contact has an inherent disadvantage in that its toroidalspring “floats” within the housing and makes connection between theterminal and housing only through physical interference. The contactsdisclosed in the present application are solidly connected (i.e.,welded) to the housing, thus improving the electrical quality of theconnection.

[0031] This invention has been described herein in considerable detailin order to comply with the patent statutes and to provide those skilledin the art with the information needed to apply the novel principles andto construct and use such specialized components as are required.However, it is to be understood that the invention can be carried out byspecifically different equipment and devices, and that variousmodifications, both as to the equipment and operating procedures, can beaccomplished without departing from the scope of the invention itself

What is claimed is:
 1. An electrical contact for use in the headerassembly of an implantable cardiac rhythm management device for matingwith a terminal pin of a tissue stimulating lead comprising: (a) a metalretainer having a base with a sidewall, an opening in the base sized toreceive a lead terminal therethrough with a predetermined non-contactclearance; (b) an electrical contact support member having an outsideshape permitting placement on an exposed edge of the sidewall of theretainer and a through hole of a diameter generally equal to that of theopening in the base of the retainer; and (c) a plurality of springmembers attached to the electrical contact support member and projectinginwardly of the diameter of the through hole of the electrical contactsupport member to provide an interference fit with a lead terminalinserted through said opening in the base of the retainer and throughthe electrical contact support member.
 2. The electrical contact as inclaim 1 wherein the plurality of spring members are attached by weldingto one of the contact support member and base of the metal retainer. 3.The electrical contact as in claim 2 wherein the spring members aregenerally shaped to provide interference with a predetermined frictionaldrag.
 4. The electrical contact as in claim 2 wherein the spring memberseach comprise a bent cylindrical bar having one end of the bar welded tosaid one of the contact support member and base and the straight sectionof the bar oriented tangent to a circle that is centered with respect tothe opening in the base, said circle being of a lesser diameter thansaid opening in the base.
 5. The electrical contact as in claim 3wherein the contact support member supports at least three of saidspring members.
 6. The electrical contact as in claim 3 wherein thecontact support member supports six of said spring members.
 7. Theelectrical contact as in claim 4 wherein the contact support membersupports at least three of the bent cylindrical bars.
 8. The electricalcontact as in claim 4 wherein the contact support member supports six ofthe bent cylindrical bars.